U.S. and South Korean forces started a 12-day joint military exercise in the region featuring combined troop strength of around 86,000 soldiers. South Korean forces described the maneuvers as defensive in nature, the Yonhap news agency reports.
The news agency published a statement from the North Korean military, however, as describing the drills as an act of war.
"As it has become clearer that the nation's sovereignty and peace which are more valuable than one's own life can be guaranteed only by arms, the army and people of the DPRK will take physical counteraction any moment, unhindered, to safeguard its sovereignty and peace," the statement read.
Victoria Nuland, a spokeswoman for the U.S. State Department, dismissed North Korea's statements as routine.
"These kinds of North Korean threats are not uncommon ... but obviously we would call on them to refrain from those kinds of bellicose statements," she said.